So have an interesting problem that developed near the end of the season this year. My Westerbeke 4.5kw Gen is slowly losing coolent somewhere. It does not appear to be leaking out of any hoses/fittings as I don't see any coolant in the bildge, however when I'm running the gen over night I find that the next day the coolant overflow bottle lost about half what was originally there. Since this is on an 2001 340DA, I was figuring it may be the heat exchanger leaking the coolant into the raw water.

Are my conclusions sound? Could I be losing the coolant elsewhere? I hooked up a coolant pressure test gauge and put (i think as thsi was end of summer) 10 psi on the system and it did slowly lose pressure over a couple of minutes.

Are there any other areas I should be checking on first as I'm sure a replacement heat exchanger will be costly?

I was actually just looking them up and they aren't as bad as I thought they were. $3-400 for a replacement. Getting to the bolts that attach them to the gen will be a joy =/ I don't think the Zinc in this gen was replaced in a while as you can't get the new one in without moving the entire exchanger as there isn't enough clearance with the floor of the bilge. Guess I should take a warm day this winter and go down and remove it to see what the damage is.